i am not sure anymore when that happened, but i am sure that worked in an earlier version of Rhino. right now each tab resizes the window automatically with no chance to resize it manually, some settings make the window so small that it does not even display the few icons on the top anymore forcing me to press the arrow button to extend the icons to switch to other settings. while there are not so many in total it would be more convenient to distribute these instead of displaying the redundant file name. the entire experience is absolutely horrifying.
A very quick test tells me that, on macOS, this behaves like that in Rhino 7 as well. This will be reworked at some point.
-wim